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        K-2

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        What's Your Hypothesis?

        Students use theories of dinosaur extinction and mammalian survival to examine the relationship between hypothesis and evidence.

        Lesson Summary

        Overview

        Young students are intrigued with dinosaurs. This lesson takes advantage of students' natural fascination with these giants of the past and explores the following questions:

        • What happened to the dinosaurs?
        • Does anyone really know for sure?
        • What is the difference between fact and fiction?

        Objectives

        • Understand that dinosaurs once lived on Earth but have completely disappeared
        • Explore the theories behind why dinosaurs are gone and why mammals survived
        • Examine the relationship between a hypothesis and evidence

        Grade Level: K-2

        Suggested Time

        Two to three class periods

        Multimedia Resources

        Materials

        • Chart paper, chalkboard, or white board
        • Colored markers, chalk, or dry erase markers
        • White construction paper
        • Crayons

        Before the Lesson

        Tell students that they are going to be investigating dinosaurs for the next few class periods. Invite them to bring in books that will help the class learn more about dinosaurs. (They will need these for Part II of the lesson.) The books should be nonfiction, so reinforce the concept that these books are based on evidence. They are different from fiction books, which have stories about dinosaurs that are often "made-up."

        The Lesson

        Part I: What Do I Know About Dinosaurs?

        1. Begin the lesson by asking students what they know about dinosaurs. Record their responses on the board or on chart paper. The students should be able to create quite a list that includes both accurate facts as well as misconceptions derived from fiction. Save the list to refer to later in the lesson.

        2. Pose the question, "How do we know dinosaurs really existed?" Allow the students to share some of their responses. Then show students the Fossilized Dinosaur Bones Flash Image, pausing at each image to discuss how what they are seeing helped scientists learn more about dinosaurs. During the discussion, lead students to the idea that what we know about dinosaurs is based on evidence.

        3. Return to the list of what students said they knew about dinosaurs. Go through each item and ask students to think about whether it is fact (there is evidence to support it) or fiction (there is no evidence to support it at this time).

        Part II: What Happened to the Dinosaurs?

        4. Ask each student to quickly share their book with the class, including one interesting fact that they learned from the book. As the students share, ask the class if that fact could be proven using evidence. Continue to reinforce the concept of fact vs. fiction (real vs. made-up). Students should now understand that dinosaurs did in fact exist, and what we know about them is based on evidence.

        5. Ask students what evidence we have that dinosaurs no longer roam Earth. Students' responses should center on the fact that no one on the planet has ever seen a live dinosaur. This will lead students to the big question, "What happened to the dinosaurs?"

        6. Introduce the word hypothesis. Explain that a hypothesis is a possible explanation of something based on facts. Scientists have been studying dinosaurs for a very long time, looking for evidence to help them figure out why the dinosaurs disappeared. However, because the evidence points to different possible explanations, no one knows for certain what happened. So, different scientists have come up with different hypotheses about what killed the dinosaurs.

        7. Project the What Killed the Dinosaurs? Shockwave Interactive on a wall screen. Navigate through the first two pages of the activity, paraphrasing the information. On the third screen is a table showing the different hypotheses scientists have about what caused the Mesozoic extinction and the evidence they use to support them. Click on the "Hypothesis" links on the left side of the table, play each animation (bottom of window), and talk with students about what different scientists think happened to the dinosaurs. Then click on the "Evidence" links at the bottom of the table and discuss each one. Finally, click on the boxes in the table to see how each hypothesis is supported by one or more types of evidence. In closing, emphasize that at this point in time, with the evidence we have, nobody really knows for sure what happened to the dinosaurs.

        Part III: How Did the Mammals Survive?

        8. Show the Mammals Get Their Chance QuickTime Video. This resource presents the most popular hypothesis of how mammals were able to succeed the dinosaurs to become a dominant life form on Earth. Discuss with the students the question posed by the video: "What if you turned back the clock?"

        Check for Understanding

        1. Review the different dinosaur extinction hypotheses presented in both the What Killed the Dinosaurs? Shockwave Interactive and the Mammals Get Their Chance QuickTime Video. Remind students that we don't know for sure which hypothesis is the right one.
        2. Next, tell the class to imagine that they have traveled back in time 65 million years to see for themselves what killed the dinosaurs. Hand out white construction paper and crayons. Instruct students to think about what they think really caused the extinction and ask them to draw their hypothesis.
        3. When they finish their drawings, ask students to describe or write a sentence explaining the evidence they have to support their hypothesis. For example: I think an asteroid killed the dinosaurs because a giant crater was found near the Yucatan Peninsula.

        The Digital Library for Earth System Education (www.dlese.org) offers access to additional resources on this topic.

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